Karl Popper (1902–1994)
Unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them. In this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise. But we should claim the right to suppress them if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols. We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant. We should claim that any movement preaching intolerance places itself outside the law, and we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal.
–Karl Popper
Critical rationalism
Against Bohr's instrumentalism, support Einstein's realism.
Let us say that, in general, failure (and disconfirmation) are more informative than success and confirmation, which is why I claim that negative knowledge is just "more robust".
Now, before starting to write this section, I spent some time scouring Popper's complete works wondering how the great thinker, with his obsessive approach to falsification, completely missed the idea of fragility. His masterpiece, The Poverty of Historicism, in which he presents the limits of forecasting, shows the impossibility of an acceptable representation of the future. But he missed the point that if an incompetent surgeon is operating on a brain, one can safely predict serious damage, even the death of the patient. Yet such subtractive representation of the future is perfectly in line with his idea of disconfirmation, its logical second step. What he calls falsification of a theory, in practice, to the breaking of the object of its application.
In political systems, a good mechanism is one that helps remove the bad guy; it's not about what to do or who to put in. For the bad guy can cause more harm than the collective actions of good ones.
Karl Popper's idea that theories can be definitely falsified, but never definitely confirmed, is yet another special case of the Bayesian rules: if
p(X|A) ~ 1, if the theory makes a definite prediction, then observing!Xvery strongly falsifiesA. On the other hand, if we observeX, this doesn't definitely confirm the theory, there might be some other conditionBsuch thatp(X|B) ~ 1, in which case observingXdoesn't favorAoverB. For observingXto definitely confirmA, we would have to know, not thatp(X|A) ~ 1, but thatp(X|!A) ~ 0, which is something that we can't know because we can't range over all possible alternative explanations. For example, when Einstein's theory of General Relativity toppled Newton's incredibly well-confirmed theory of gravity, it turned out that all of Newton's predictions were just a special case of Einstein's predictions.
–Eliezer Yudkowsky
Stephen Hawking erroneously referred to Popper as positivist:
Any sound scientific theory, whether of time or of any other concept, should in my opinion be based on the most workable philosophy of science: the positivist approach put forward by Karl Popper and others. According to this way of thinking, a scientific theory is a mathematical model that describes and codifies the observations we make. A good theory will describe a large range of phenomena on the basis of a few simple postulates and will make definite predictions that can be tested. … If one takes the positivist position, as I do, one cannot say what time actually is. All one can do is describe what has been found to be a very good mathematical model for time and say what predictions it makes.
However, the claim that Popper was a positivist is a common misunderstanding that Popper himself termed the "Popper legend".[55] In fact, he developed his beliefs in stark opposition to and as a criticism of positivism and held that scientific theories talk about how the world really is, not, as positivists claim, about phenomena or observations experienced by scientists.[56] In the same vein, continental philosophers like Theodor Adorno and Jürgen Habermas regarded Popper as a positivist because of his alleged devotion to a unified science. However, this was also part of the "Popper legend"; Popper had in fact been the foremost critic of this doctrine of the Vienna Circle, critiquing it, for instance, in his Conjectures and Refutations.